The Obligitory High School AU
by Mother Of The Universe
Summary: Every fandom has an obligatory high-school Au. This is Undertale’s. Frisk is the misunderstood new kid. Sans, Papyrus, Undyne, and Alphyse are the odd friend group that takes them in. All of them deal with teen angst, especially freshman Frisk and Papyrus, still recovering from middle school. Let the adventure begin.


Ever notice how every fandom seems to have the obligatory High School AU?

This is Undertale's.

~

The laundry hamper was on the top shelf. If he was tall, like his dad and younger brother, then he would've been able to reach it with ease. But no, he had to have his growth stunted at 5 feet. He had to be _short_.

All Sans wanted was his hoodie, which sat in the basket on the top shelf. His brother had insisted on washing it, but Sans kept stealing his hoodie back whenever he had the chance.

That was two months ago.

Yeah, the hoodie did need to be washed. Desperately. But the teenager didn't want to let it go for any amount of time. And now, it was the first day of a new school year, and Sans desperately wanted to wear the thing, but no! His little brother had to place it in the laundry basket on the top shelf.

He was going to _kill_ Papyrus.

With no other option, Sans checked to make sure his brother wasn't around, before attempting to climb the shelf. As he predicted, the shelf fell down, making a large crashing sound, leaving the contents scattered across the floor, and Sans with a large bump on his skull.

His hands gripped his hoodie. Mission successful.

"SANS!" A loud voice shouted. Sans winced, the volume causing his head to throb. Feet stomped to the door of the laundry room. Sans shook the fog out of his head, and looked at his brother, standing in the door way.

While Sans growth had been stunted, Papyrus had seemed to shoot up like a bean sprout. He was only 15 years old, and had already reached the large hight of 6'10. And he was still growing. He was a skeleton, like his brother, though his head shape was different than Sans, being something of a jaw attached to a circle, while Sans scull was a squat structure, built with a perminent smile. Papyrus stood with what could only be described as a pout. Sans held back a giggle. He could tell his baby brother was trying to glare at him, but it was very ineffective.

"yeah bro?" Sans replied smoothly, a smirk in his voice. His brothers pout seemed to deepen.

"YOUR NOT WEARING THAT HOODIE TO SCHOOL! IT HASN'T BEEN WASHED IN MONTHS!"

Sans rolled his eyes, looking at the outfit Papyrus had chosen to worn for his first day of Freshman year in high school. It was eccentric, to say the least. One look at the lime green crop top with small basketballs as sleeves, the short blue shorts, and his bro's signature red boots, gloves, and scarf, screamed off warning bells in the big brothers head that this outfit was going to get him teased. He was bullied horribly in middle school. Sans didn't want the same thing to happen now.

"Uh, you wearing that to school?" Sans asked, wearily, careful not to hurt his brothers feelings. The question made Papyrus look insecure, as the young teen fumbled with his hands, avoiding eye contact.

"Yeah," he spoke quietly. Sans felt a pant of guilt in his stomach. "I was saving it for a very special occasion, and I'll finally be going to school with you again, so I though that..." he continued to wring his hands, nervously. His big brothers opinion meant the world to him, even if he sometimes suspect Sans was lying to him to make him feel better. "Do you... not like it?"

"nah, bro!" Sans declared with a smile. "that outfits pretty cool. i'm just worried your going to outcool everyone else in class!"

Papyrus was suspicious of the answer, but decided to take it anyways. "OF COURSE!" He declared, his voice retaining its normal volume. "I, THE GREAT PAPYRUS, WILL OUTCOOL EVERYONE! I'LL BE SO COOL, EVERYONE IN CLASS WILL WISH TO BE MY FRIEND! NYE HEHEH!"

"course, bro" Sans replied. This year was going to be better. Even if Papyrus couldn't make his own friends, he could always hang with him. Besides, Sans friends all loved Papyrus. Undyne, a childhood friend of both Sans and Papyrus, who was a year above the older of the two, was like a big sister to them. So much so that she had threatened to beat up the entire middle school when she found out Papyrus had been getting bullied. Her "not girlfriend" Alphyse enjoyed the young skeleton as well, finding his enthusiasm in everything pretty comforting. His pall Grilby seemed to be ok with everyone, and there where plenty of other friends of Sans that Papyrus didn't know yet. As long as nobody teased or bullied him. And if they did, they would get football captain Undyne ready to beat their ass. Not to mention Sans proficient skills in blackmail.

Much to the younger skeletons dismay, Sans put the unwashed hoodie on over his T-shirt. The two brothers then ate breakfast (bacon and eggs, cooked by their dad before he left for work), and left the house, armed with their backpacks and books.

Five minutes after stepping outside, an old, beat-up green convertible drive up to their house, where their friend, Undyne, sat in the drivers seat. She was wearing a simple tank top and jeans over her blue, fish scaled skin. Red fins sprouted over the top of her head like hair, which where slightly torn, as where the fins that sat in place of ears, courtesy of years of roughhousing. She flashed them a smile full of sharp, yellow teeth, similar to those of anglerfish. Her single gold eye held excitement, with the other one covered by a black eye patch after she had lost it a few years prior. She honked the horn several times.

"Get in, Goobers!" She shouted, calling them the nickname she had given them back when they where little kids. "We're going to school!"

Sans hopped into the back seat, while Papyrus struggled to lock the door.

"Not like I'm one to talk, considering my fashion sense is dead," Undyne whispered to the older skeleton. "But I'm pretty sure what he's wearing screams 'pick on me'"

Sans shrugged warning off. "He'll be fine. He's got us,"

"Yeah, but unlike you, Pappy cares about what other people think of him," Undyne replied, concerned. High schoolers where more mature than Middle Schoolers, but people could still be mean.

Papyrus got into the front seat, which Undyne had reserved for him. It occurred to Sans that he really needed to learn how to drive...

~

The high school of Undertown didn't look like much, but the faculty did their damnest to make Undertown High School the best it could possibly be.

Sans would be a Junior, and Undyne would be a Senior. Which meant applying to colleges and getting good grades. Undyne had known since she was little that she wanted to go into the police academy. She ended up selling Papyrus on the idea, even though the young skeleton seemed more artistically inclined. Sans had wanted to go into the field of science, much like his father, but after what his brother went through in middle school, Sans had started to loose interest.

In fact, Sans didn't take much an interest in anything anymore.

Undyne pulled up to the front of the school, her old car letting out a pop and a bang as she turned off the grubby engine. The car was years past it's retirement age, but Undyne hasn't bothered to buy a new one.

Papyrus ran forwards towards the school, a happy little skip in his step. His smile radiated sunshine, and his enthusiasm was contagious. Sans sighed happily as he watched his baby brother bounce happily as if he had entered heaven. As a kid, Papyrus had loved school. It was a relief to see that the bullying in middle school hadn't taken that away.

Undyne felt a swell of pride as Papyrus shouted at them to get out of the car and get to the school. She glanced at Sans, who was also wearing the same prideful expression. "Our Goober is growing up," she declared. Sans nodded in agreement.

~

"Slow down, nerd!" Undyne commanded as Papyrus practically dragged her and Sans to the school gym, where first-day-of-school announcements would be made. He was completely oblivious to the few students who snickered nastily at his outfit, though Sans and Undyne weren't. Sans had made sure to send a particularly angry glare in the direction of some of the kids who had bullied Papyrus the year before. They didn't even have to see Sans glare or Undyne vicious scowl at them to know that they where on the two kids BAD LIST!

Everyone entered the stadium and settled down in their seats. It was sorted by grade, so the three had to separate, unfortunately, though, thanks to his hight, Sans could still see Papyrus from where he was at. He was already chatting up a storm with an unfamiliar face next to him, though said face didn't seem appreciative of the conversation. At least they where being nice.

Letting out a sigh of relief, Sans took his own seat. He was soon joined by his pal Grilby, a living piece of fire, who wore glasses and plain clothes over his orange flames.

"sup, grilb's?" Sans greeted the kid. Grilby sat down next to Sans before speaking, his voice quiet and mumbly, further made hard to understand with his thick foreign accent.

"You still owe me money," Grilby reminded Sans. So much for a friendly greeting.

Sans feigned ignorance. "what'chu talkin' 'bout, grilbs," Sans drawled, ignoring the fire monsters unamused stare. "i _never_ owe anyone money for anything,"

That was a lie. The year before, Undyne had tried to teach Papyrus how to cook, but she was absolutely terrible at it. In turn, Papyrus ended up being a terrible cook because of her, though Sans, like with many things, didn't have the heart to tell his brother the truth about his horrible cooking. So Papyrus would cook lunch for Sans. Every day. And Sans would throw it out and tell his brother he ate it. Every day. So Grilby would give Sans money to but lunch. Every day. And now, Sans owed his pal a _lot_ of money.

Thankfully, Sans wasn't left under the heat of Grilby's glare for too long. The school principle; a beautiful goat monster named Toriel, had gotten up on stage and began to make the start of the year announcements.

"Greetings, students," she called to the students in her melodic voice, making all the teens in the room feel calmed and safe. "Today marks the beginning of a new school year, and I must say, I for one, am very excited to spend it with all of you. Now, before I say my usual welcomes and speeches, I've got an important announcement to make. This year marks the start of something special, because this year, a _human_ has joined our freshman class!"

Everyone was silent. Some kids looked curious, some excited, and some angry. It was well known that humans and monsters didn't get along, and tried their damnest to stay the hell away from eachother. But now, a human would be joining them in their school.

Sans pittied the poor kid.

Toriel glanced at all the quiet children nervously, wondering what each child was thinking. She didn't expect every kid to take the news well. But she was hoping that at least _some_ of the kids would've shown some level of enthusiasm. Without much else to say, she called the human to come to the front of the room.

The kid was small, and skinny, their short, dirty-brown hair covered their eyes, and the fairy-blue knitted romper they where clothed in looked at least a few sizes too big for them. They wore a pair of black boots, and their face and knees had band-aids on them. Their skin held a yellow tint to it. It was hard to tell wether the kid was a boy or a girl.

Toriel invited the small kid up to the podium to introduce themselves.

"H-hi," the kid almost whispered into the microphone. They where shaking, obviously anxious and terrified. They looked out at the crowd of dozens upon dozens of monsters, most of them giving her angry glares, or blank stares. Sans spotted Papyrus, smiling a bit to see that he was excited to meet the human. At least _he_ would be nice to them.

"M-my name is Frisk," the kid said. "I'm gonna be in, uh, ninth grade, uh..." their voice was tiny, with a higher pitch to it. There was no confidence in it. "I-I'm 14. And, um..." they looked down at the floor, letting their messy bangs hang over their eyes. "I'm, um, I'm t-t-technically a girl, b-but, uh, I would, um, really appreciate it if, uh, you all used... if you all used they/them pronouns... f-f-for m-me,"

They're declaration of being non-binary seemed to take physical energy to say. If Sans had to take a guess why, it would be because humans where less accepting of gender preferences, at least from what he heard.

At certain points in a Monsters life, they may start to feel unhappy with the gender they where born with. Due to most monster physiology, changing ones body for maximum self-comfort was normal. It was called a Changing.

Not all monsters could Change. Though, desiring a Changing was uncommon, so it was unlikely that if one couldn't Change, they would want to at all. Humans obviously couldn't Change. So Frisk, despite being non-binary, would be stuck being pure female, at least for a while.

Of course, Monsters didn't really care about Changings. There wasn't much reason to be bigoted like that. It was rather pointless, in the end. But humans seemed to lack the ability to mind their own business that monsters had.

Seeing that nobody was going to get angry at that announcement, Frisk took a deep breath and continued, feeling much better now that they had gotten that announcement out of the way.

"Um, I'm from a place in America called Chicago," they continued to speak. "I've been in foster homes for a while now, but Mom— I mean, Miss Toriel decided to adopt me, so, now I'm living here, in Undertown. I'm excited to be here! E-everyone I met so far seems so nice! A-and, I know that, uh, monsters and humans don't always get along, b-but, I think— I think that... if you give me a ch-chance, then I can show you, th-that humans, maybe, aren't s-so bad!"

When they finished, their yellow knuckles had turned white from gripping the podium so hard. The poor kid looked as if they where about to faint.

As soon as he was sure the human was done speaking, Papyrus stood up and started clapping. "GO HUMAN!" He cheered, giving the poor kid his brightest smile. To Papyrus, they seemed friendly. Maybe a bit shy, but that was why they would need a good friend. He could be that friend, if the human wanted him to, that was.

Frisk turned red, and smiled, obviously happy that _someone_ liked their first impression.

Even if he was the only one who had started clapping.

Papyrus soon noticed this, and looked around at all the other kids in the school, still glued to their seats. He looked a little disappointed in them, but that soon turned to a look of embarrassment and shame when he noticed some of the kids where glaring at him. He spotted Undyne in the crowd, and noticed that she was wearing the face she had when he made a big social blunder, and she was wondering how she was going to fix it this time.

Humiliated, Papyrus sat down.

It was up to Sans and Undyne to fix this.

Undyne didn't really like humans. She didn't like that a human was now invading her school. The kid didn't seem malicious, yet, but Undyne was suspicious. Maybe a good glare and a verbal warning was all the kid would need to keep from trying anything, but Undyne couldn't be sure.

Sans, on the other hand, couldn't really care less about the human. If they messed with his friends, he'd kick their ass, as he would anyone, human or monster, and if the kid somehow wormed their way into his heart, which was unlikely, but not impossible, then Sans would protect them, as any friend would. But for now, to him, this kid was just another student. He always felt too lazy to really clap for anyone, no matter who they were.

But both knew that the kids in the school, especially the ones who where glaring at Frisk as if they killed their dog, probably wouldn't take Papyrus' little social blunder that well.

So they started clapping too. And seeing the school football captain clap encouraged other students to do so, and soon it caught on. Everyone clapped for the human. Papyrus eagerly joined in once people had stopped glaring at him for his actions, and Frisk smiled brightly on stage, seeming a little bit more confident in themselves.

Toriel took the podium once again, and started to continue with the normal announcements givin at the beginning of every school year; new classes, new teachers, teachers about to retire, and so on. Sans didn't listen to any of it, choosing to fall asleep instead. He ended up drooling on Grilbys shoulder; an action not appreciated.

The kid who Papyrus had been talking to earlier had moved after he had clapped for the human, leaving a spare seat. Knowing their chances of sitting next to someone who despised them would decrease if they sat next to the poor Freshman who clapped first, Frisk decided to choose that spot to put themselves.

Now that they where next to the skeleton, they noticed how much he towered over them. They had stopped growing at the sad hight of 4'12", and sitting next to the beanpole teen made them feel shorter. They noticed the bizarre fashion choice, and instantly felt respect for the skeleton. It took a lot of confidence to pull off something like that, and while he looked a tad bit dorky, pull the outfit off he did. Frisk smiled at him, wondering if he would protect them from bullies or just let them pummel them, or even worse, join in on it. They dared to find out.

"Thank you," Frisk whispered to the teen next to them. "For giving me support,"

"HUH," Papyrus mumbled in surprise, not having expected the human to talk to him. "Oh! That was no problem!" He enthusiastically exclaimed, keeping his volume low. "The Great Papyrus always makes an effort to make people feel welcome!"

Frisk giggles at his statement. They where right about him being confident.

Papyrus continued. "After all, someone with many friends must be prepared to make new ones, and that's what I will be by the end of this year! Someone with many, many friends!"

There was something sad about that statement, but Frisk decided not to pry into the personal life of a guy they just met.

"S-so," Frisk mumbled. They knew it was rude to talk while there was a speach going on, but they didn't want to stop. It was a rare thing for Frisk to make friends. They didn't know if the teen next to them would end up being their friend, but at least he was willing to try. They weren't going to loose an opportunity like this. "What- uh... what do you like to do?"

Papyrus's eyes seemed to glow in happiness. Someone wanted to know about him! What more could a skeleton ask for?

And so Papyrus went on a long rant about puzzles, and how much he loved them. He told his new classmate stories of how he had been drawing and solving them since he was a kid, the pure joy they could give him, and how he had never met anyone who liked puzzles as much as he did.

And Frisk hung on to every word. While they didn't hold as much enthusiasm for puzzles as the skeleton seemed to, they had always enjoyed them. Rubix cubes, crosswords, riddles, and the like. And so they listened to Papyrus's rant.

Frisk themselves wasn't much of a talker, so they enjoyed a friend who would do the talking for them. They loved to listen to the stories and tales of others. Curiosity was one of Frisk strengths, and learning about people satisfied such curiosities. And every word the skeleton spoke just made them even more curious about him. What where the puzzles he made? What where the puzzles he solved? How did he make and/or solve them? Why did he love puzzles so much? And every detail of his life that he accidentally revealed gave Frisk more questions. Why did he look sad whenever he mentioned middle school? Why did he talk about his dad being proud of him as if it rarely ever happened? He mentioned being in 7th grade for two years. Did he have to repeat that year? Why was that? He talked about his brother a lot. And a childhood friend of his named Undyne, who was like his sister. What where they like?

Frisk wanted to know everything about him. How he revealed so much yet so little about himself at the same time. It was fascinating.

He was so _fun_ to listen to!

"... though, if you don't like puzzles, I suppose I should stop talking about them..." He ended, sounding ashamed for talking so much. He wasn't the most observant ever, so it was hard for him to know when people wanted him to stop talking to them. But his dad had told him that nobody likes to listen to his long rants.

"N-no!" Frisk said quickly, worried that if he stopped talking now, he wouldn't talk to them again. He couldn't stop, not when Frisk had so many questions about him! They had to know everything about him.

And for some reason, Frisk felt as if they didn't mind if the sweet, energetic chatterbox sitting next to them learned everything about them, either.

"I like puzzles," they told him. "Tell me more,"

Papyrus practically radiated sunshine. Not only did the human seem to enjoy listening to them, but, they told him to keep going! He felt so happy, it took all the strength in his bones not to joyously hug the human teen.

So he continued, bouncing in his seat like a little kid. And Frisk continued to listen, even asking questions every so often.

And Sans watched his brother joyously smile and act more bubbly than he'd seen him in years. He had never seen Papyrus smile like that. Not after Middle school at least. But now...

Papyrus and Frisk would leave the gym as friends.


End file.
